Vapor compression systems are commonly used for refrigeration and/or air conditioning and/or heating, among other uses. In a typical vapor compression system, a refrigerant, sometimes referred to as a working fluid, is circulated through a continuous thermodynamic cycle in order to transfer heat energy to or from a temperature and/or humidity controlled environment and from or to an uncontrolled ambient environment. While such vapor compression systems can vary in their implementation, they most often include at least one heat exchanger operating as an evaporator, and at least one other heat exchanger operating as a condenser.
In systems of the aforementioned kind, a refrigerant typically enters an evaporator at a thermodynamic state (i.e., a pressure and enthalpy condition) in which it is a subcooled liquid or a partially vaporized two-phase fluid of relatively low vapor quality. Thermal energy is directed into the refrigerant as it travels through the evaporator, so that the refrigerant exits the evaporator as either a partially vaporized two-phase fluid of relatively high vapor quality or a superheated vapor. This thermal energy is often sensible and/or latent heat that is removed from a flow of air in order to condition that flow of air prior to delivering the air to the temperature and/or humidity controlled environment.
At another point in the system the refrigerant enters a condenser as a superheated vapor, typically at a higher pressure than the operating pressure of the evaporator. Thermal energy is rejected from the refrigerant as it travels through the condenser, so that the refrigerant exits the condenser in an at least partially condensed condition. Most often the refrigerant exits the condenser as a fully condensed, sub-cooled liquid.
Some vapor compression systems are reversing heat pump systems, capable of operating in either an air conditioning mode (such as when the temperature of the uncontrolled ambient environment is greater than the desired temperature of the controlled environment) or a heat pump mode (such as when the temperature of the uncontrolled ambient environment is less than the desired temperature of the controlled environment). Such a system may require heat exchangers that are capable of operating as an evaporator in one mode and as a condenser in an other mode.
One especially useful type of heat exchanger used in some refrigeration systems is the parallel flow (PF) style of heat exchanger. Such a heat exchanger can be characterized by having multiple, parallel arranged channels, especially micro-channels, for conducting the refrigerant through the heat transfer region from an inlet manifold to an outlet manifold.